This invention relates to compression-assembled semiconductor devices, and more specifically relates to a novel construction for such devices which simplifies the pole piece assembly and which prevents breakage of gate leads due to movement of the semiconductor device within the assembly when the pole pieces are not under compression forces.
Compression-assembled semiconductor devices are well known and are typically shown in U.S. Pat. Nos. 3,452,254 to Boyer, 3,489,957 to DeWarga and 3,681,667 to Kokosa. Devices of this type are used primarily to form semiconductor devices of extremely high power capabilities and which make electrical connection to opposite semiconductor device surfaces by massive opposing pole pieces which bear on the semiconductor device with high pressure.
The advantages and constructional details of these devices are well known in the art. When the semiconductor device in the package has a gate lead as for a thyristor or triac type semiconductor device, the gate lead is a thin, fragile wire which is electrically connected to a gate lead electrode which extends externally of the package, but must not touch the pole pieces.
When the pressure-assembled device is not under high compression forces, the semiconductor device may be relatively loosely held within the package and thus may move or rotate relative to the package when the package is moved or jarred. If this should happen, the gate lead of the device may break or touch one of the pole pieces and the device will not function, or will fail.
One aspect of the present invention deals with a novel manner of immobilizing and centering the semiconductor device within the assembled package even though the package is not subjected to compression loading.
A further problem which is encountered in the manufacture of compression-assembled devices is the need for a configuration which permits the centering of the two relatively massive electrodes relative to one another and relative to the wafer configuration before their cooperating flanges are welded or otherwise secured to one another. Prior art constructions use relatively expensive and complex forming techniques for forming the cooperating circular flanges secured to the electrodes so that they can nest relative to one another when they are assembled, thereby to automatically center their main electrodes relative to one another, with some additional means to center the wafer.
A further aspect of the present invention lies in an inexpensive construction for the flanges which permits the flanges to be easily and properly centered relative to one another during the assembly operation.
The invention is also applicable to rotationally non-symmetrical wafer configurations with peripheral amplifying gates, and permits rotational alignment of the wafer relative to pole pieces.